The CoSb3 (skutterudites) based materials are promising candidates as thermoelectric materials for the middle temperature range. Several research reports have been published on skutterudites and have reported high figure of merit (ZT) [1-4], with a major feature of these materials being the filling of voids with Alkaline earth metals or Rare Earths. This helps to decrease the thermal conductivity by phonon scattering due to rattling of the guest atom . But a disadvantage is the air sensivity of these guest atoms, which makes the processing difficult, especially on the bulk scale and their elevated price, making the bulk producers think of alternatives.
We report here CoSb3-based thermoelectric materials doped with Si and Te simultaneously. This helped, not only in lowering the thermal conductivity but also produced a high power factor (>4 mW/m*K2). And an attractive ZT for Rare earths-free skutterudites is found.
High density materials were prepared by solid state synthesis followed by grinding, compacting in Cold Isostatic Press (CIP), sealing, reannealing and then sintering in Spark Plasma Sintering (SPS) under Argon atomosphere. Crystallographic analysis and thermoelectric properties of all the samples are presented.
 G. Rogl, P. Rogl, E. Bauer and M. Zehetbauer, in "Thermoelectric Nanomaterials", eds. K. Koumoto and T. Mori (Springer, Heidelberg, 2013) p. 193-254.
 X. Shi, J. Yang, J. R. Salvador, M. Chi, J. Y. Cho, H. Wang, S. Bai, J. Yang, W. Zhang, and L. Chen, J. Am. Chem. Soc. 133, (2011), p. 7837-7846.
 M. W. Gaultois, T. D. Sparks, C. K. H. Borg, R. Seshadri, W. D. Bonificio, and D. R. Clarke, Chem. Mater. 25, (2013), p. 2911?2920.
 Jing-Feng Li1, Wei-Shu Liu1,2, Li-Dong Zhao1,2 and M. Zhou, NPG Asia Materials 2, (2010), p. 152-158.
 G. S. Nolas, D. T. Morelli, T. M. Tritt, Annu. Rev. Mater. Sci. 29, (1999), p. 89-116.
National Institute for Materials Science
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